It’s on page 22:
Immediately before the combat is resolved, any defending artillery
present in the attacked territory can make a pre-emptive strike against all of
your offloading land units and fighters as they come ashore.
Surviving attacking units then land in the territory and move on to land combat.
The land combat is conducted in the same manner as any other land combat with one exception. If there was no sea battle, any battleships that are in the sea zone(s) from which units offloaded from transports can conduct offshore bombardment.
The bolded segment states that there’s no difference to the land combat with the remaining land units preventing the artillery from defending. If there were, they would have to specify “don’t put defending artillery on the battle board” or something along those lines.